1. Field of the Invention
This disclosure relates to novel compounds that can be used as crosslinkers to cure polyorganosiloxanes.
2. Description of the Prior Art
The reaction between a polyorganosiloxane containing aliphatic unsaturation and an organohydrogensiloxane in the presence of a catalyst is well known in the art. The reaction essentially involves the establishment of a new Si--C bond according to the following abbreviated equation: ##STR2## and is elaborated in U.S. Pat. No. 2,823,218, issued February 11, 1958, to Speier et al.
The polyorganosiloxane will typically have an average of from one to three organic substitutions per silicon atom. Representative organic substituents include saturated and unsaturated monovalent aliphatic radicals, monovalent halohydrocarbon radicals and aryl radicals.
A polyorganosiloxane frequently used in the preparation of siloxane elastomers is poly-3,3,3-trifluoropropylmethylsiloxane. Elastomers made from this fluorinated siloxane exhibit unique swelling characteristics in many solvents and oils. This siloxane can be modified with vinyl substituents which will allow it to cure according to the previously described addition reaction.
Crosslinkers having an .tbd.SiH function and previously used to cure polyorganosiloxanes having unsaturated aliphatic functions include mixtures of the following: EQU CF.sub.3 (CH.sub.2).sub.2 Si(OSiMe.sub.2 H).sub.3
and EQU CH.sub.3 (CH.sub.2).sub.2 {SiO(OSiMe.sub.2 H).sub.2 }.sub.x Si(OSiMe.sub.2 H ).sub.2 (CH.sub.2).sub.2 CF.sub.3
wherein x is equal to 1 or 2 and Me represents methyl.
In most instances, these compounds react and cure satisfactorily, but there are some problems. For example, CF.sub.3 (CH.sub.2).sub.2 Si(OSiMe.sub.2 H).sub.3 is more volatile than desired. Furthermore, these compounds are most easily made from the hydrolysis and condensation of silanes such as Me.sub.2 HSiCl and CF.sub.3 (CH.sub.2).sub.2 SiCl.sub.3, and the products suffer from a lack of reproduceability.